One type of package for premoistened wet wipers is described in U.S. Pat. No. 3,904,074, issued Sept. 9, 1975 to L. S. Hoffman, et al and assigned to the assignee of the present invention. The container is generally rectangular in shape but has rounded corners. The premoistened wet wipers are placed inside the container and a moisture-impervious sheet of foil is adhered to the opening of the container to prevent loss of moisture from the package. After a consumer purchases the wet wiper product, the foil seal is broken to gain access to the wipers and resistance to moisture loss from the package is obtained from the cooperation of the closure and the container. If the rate of moisture evaporation from the package is relatively high compared to the rate of usage of the wiper product, some of the wipers will dry out and will not be of any use to the consumer. In such cases it would be desirable to have secondary sealing means between the closure and the container body which will retard moisture evaporation from the package after the foil seal has been broken.
One possible solution to the above described problem is to employ a continuous sealing fin, inclined from the top wall of the closure, which seals against a lip surrounding the container opening. The use of such continuous fins to provide a seal between a closure and a container having a circular opening are well known in the prior art. Thus, U.S. Pat. Nos. 3,055,526--Plunkett, 3,151,757--Martin, 3,200,981--Harding and 3,255,909--Miller et al, all disclose the use of a threaded cap having a continuous, annular fin seal that is inclined with respect to the top wall of the closure to seal the annular opening of a container. The continuous, inclined, annular fin seal as represented by the patent to Miller et al functions by (1) bending or hinging at the junction of the fin and the top wall of the closure and by (2) circumferential stretching of the fin as it is compressed against a mating annular surface of the container. U.S. Pat. No. 3,215,297--Acton et al discloses a threaded container closure having two concentric, continuous fin seals for sealing the annular opening of a container. U.S. Pat. No. 3,286,866--McIntosh discloses a threaded closure having two concentric, continuous, annular fin seals, the inner fin seal being inclined with respect to the top wall of the closure and providing sealing of an annular opening of a container. U.S. Pat. No. 3,720,342--Vercillo, discloses a safety closure that interlocks with the container, the closures having a continuous annular fin that is inclined with respect to the top wall of the closure and which seals an annular opening of the container.
The packaging system described in the patent to Hoffman et al has been designed so that a relatively small force is required to apply and retain the closure over the container. If the packaging system of Hoffman et al is adapted to include a continuous fin seal as taught by the prior art, it would be necessary to apply a significantly large closing and retaining force to the cover in order to provide and maintain the required circumferential stretching of the continuous fin seal to achieve effective sealing of the package.